1. Statement of the Technical Field
The inventive arrangements relate generally to the field of capacitors, and more particularly to capacitors embedded in a substrate.
2. Description of the Related Art
Embedded capacitors are currently available in both printed wire board (PWB) and low temperature co-fired ceramic (LTCC) technologies. Typically, printed conductors are deposited on a substrate and used as electrodes for a capacitor. In some instances, the substrate itself can serve as the dielectric for the capacitor. In other arrangements, a via within the substrate can be filled with a dielectric material.
Using LTCC, the printed conductors are typically created using a printed thick film process. Etching processes are typically used for PWB's. In either case, forming capacitors with tight tolerances can be difficult. In particular, it is often difficult to precisely control the area of the electrode. A small difference in electrode area can significantly change the capacitance of a part.
This problem is compounded further when trying to simultaneously create both high and low valued capacitors on a substrate. In such circumstances, high permittivity dielectrics are typically used so that high value capacitors can be formed in a volumetrically efficient manner. But the use of the high permittivity dielectrics requires that very small electrodes be used to achieve small value capacitors. Maintaining a tight tolerance on such electrodes can be extremely difficult. For example, when printing electrodes on LTCC, variables such as bleed-out, mesh density, and inaccuracies in the printing process each contribute to dimensional inaccuracies of the electrodes. Accordingly, a solution is needed for creating embedded capacitors wherein tight tolerances can be maintained over a large range of capacitance values.